.TH std::num_put 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::num_put \- std::num_put

.SH Synopsis
   Defined in header <locale>
   template<

       class CharT,
       class OutputIt = std::ostreambuf_iterator<CharT>

   > class num_put;

   Class std::num_put encapsulates the rules for formatting numeric values as strings.
   Specifically, the types bool, long, unsigned long
   , long long, unsigned long long
   \fI(since C++11)\fP, double, long double, void*, and of all types implicitly convertible
   to these (such as int or float) are supported. The standard formatting output
   operators (such as cout << n;) use the std::num_put facet of the I/O stream's locale
   to generate text representation of numbers.

   std-num put-inheritance.svg

                                   Inheritance diagram

   If a std::num_put specialization is not guaranteed to be provided by the standard
   library (see below), the behaviors of its put() and do_put() are not guaranteed as
   specified.

.SH Specializations

   The standard library is guaranteed to provide the following specializations (they
   are required to be implemented by any locale object):

   Defined in header <locale>
   std::num_put<char>    creates narrow string representations of numbers
   std::num_put<wchar_t> creates wide string representations of numbers

   In addition, the standard library is also guaranteed to provide every specialization
   that satisfies the following type requirements:

     * CharT is one of
          * char,
          * wchar_t, and
          * any other implementation-defined character container type that meets the
            requirements for a character on which any of the iostream components can be
            instantiated; and
     * OutputIt must meet the requirements of LegacyOutputIterator.

.SH Member types

   Member type Definition
   char_type   CharT
   iter_type   OutputIt

.SH Member functions

   constructor   constructs a new num_put facet
                 \fI(public member function)\fP
   put           invokes do_put
                 \fI(public member function)\fP

.SH Protected member functions

   destructor   destructs a num_put facet
                \fI(protected member function)\fP
   do_put       formats a number and writes to output stream
   \fB[virtual]\fP    \fI(virtual protected member function)\fP

.SH Member objects

   static std::locale::id id id of the locale
                             \fI(public member object)\fP

.SH Example


// Run this code

 #include <iostream>
 #include <iterator>
 #include <locale>
 #include <string>

 int main()
 {
     double n = 1234567.89;
     std::cout.imbue(std::locale("de_DE.UTF-8"));
     std::cout << "Direct conversion to string:\\n"
               << std::to_string(n) << '\\n'
               << "Output using a german locale:\\n"
               << std::fixed << n << '\\n'
               << "Output using an american locale:\\n";

     // use the facet directly
     std::cout.imbue(std::locale("en_US.UTF-8"));
     auto& f = std::use_facet<std::num_put<char>>(std::cout.getloc());
     f.put(std::ostreambuf_iterator<char>(std::cout), std::cout, ' ', n);
     std::cout << '\\n';
 }

.SH Possible output:

 Direct conversion to string:
 1234567.890000
 Output using a german locale:
 1.234.567,890000
 Output using an american locale:
 1,234,567.890000

   Defect reports

   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.

      DR    Applied to        Behavior as published              Correct behavior
                       num_put was guaranteed to accept any only guarantees to accept
                       CharT that                           char,
   LWG 427  C++98      meets the requirements for a         wchar_t and other
                       character on which                   implementation-
                       any of the iostream components can   defined character types
                       be instantiated
                                                            can guarantee to accept
   LWG 2392 C++98      only character type CharT could be   implementation-
                       guaranteed to be accepted by num_put defined character container
                                                            types

.SH See also

   numpunct   defines numeric punctuation rules
              \fI(class template)\fP
   num_get    parses numeric values from an input character sequence
              \fI(class template)\fP
   to_string  converts an integral or floating-point value to string
   \fI(C++11)\fP    \fI(function)\fP
   to_wstring converts an integral or floating-point value to wstring
   \fI(C++11)\fP    \fI(function)\fP
